Title: #1015: proxy: allow proxy provider to start without having proxy_resolver_lib_name
Proxy provider fails to start unless `proxy_resolver_lib_name` is set
since recent hosts resolver addition. This would impact all existing
proxy provider configurations.
This patch makes sure that proxy resolver is disabled if the option
is not set but other functions are not affected.
To pull the PR as Git branch:
git remote add ghsssd https://github.com/SSSD/sssd
git fetch ghsssd pull/1015/head:pr1015
git checkout pr1015